PubMed · 6688047
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H R Lieberman. 1983. Estimating LD50 using the probit technique: a BASIC computer program.. https://doi.org/10.3109/01480548309072465
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In the future, extrapolation procedures will become more and more important for the effect assessment of compounds in aquatic systems. For achieving a reliable method these extrapolation procedures have to be evaluated thoroughly. As a first step three extrapolation procedures are compared by means of two sets of data, consisting of (semi)chronic and acute toxicity test results for 11 aquatic species and 8 compounds. Because of its statistical basis the extrapolation procedure of Van Straalen and Denneman is preferred over the procedures of the EPA and Stephan et al. The results of the calculations showed that lower numbers of toxicity data increase the chance of underestimating the risk of a compound. Therefore it is proposed to extend the OECD guidelines for algae, Daphnia, and fish with chronic (aquatic) toxicity tests for more species of different taxonomic groups.
The Hill equation, mi = Mmax/(1 + [Ti/t]ni), describes the mortality (mi) versus time (t) of a normal or an intoxicated organism. Parameters Ti and ni are, in turn, functions of doses (di) of toxin, according to the same equation. Doses dT50 and dN50 eliciting a half-maximum variation of parameters Ti and ni are both fundamental toxicological constants. The tangents (delta i) to the curve of mortality vs time also obey the same type of equation and allow an additional family of constants, d delta 50, to be derived. In contrast, LD50 varies between zero and infinite. The model can be readily generalized to the opposite phenomena involving a stimulation of the life span of organisms.
Knowledge of the acute toxic effects of chemicals is important for the protection of exposed humans. Since sufficient information in humans is often lacking, experiments on laboratory animals must be performed. The LD50 test, which requires large numbers of animals, has become the preferred procedure. It is now widely criticized on scientific and ethical grounds. This paper reviews the possibilities of using fewer animals to obtain relevant information on the acute hazards of chemical substances, but it also identifies the reasons why the traditional testing approaches cannot be changed immediately. An important problem is the practice of basing legal decisions on classification of chemicals in official lists of hazardous substances and for labeling purposes on LD50 values. Proposals are presented on how pain and suffering of the animals included in acute toxicity tests can be reduced. The use of in vitro systems for the evaluation of the hazardous properties of chemicals is discussed.